1. Field of the Invention
The invention relates to extracorporeal hemodialysis and more particularly to method and apparatus for dialyzing a patient's blood with a single venipuncture or cannulation.
2. The Prior Art
Historically, kidney diseases have been of critical concern to human life. Many kinds of kidney diseases interfere with the function of the kidney such that the kidney ceases to remove waste and excess water from the blood. When the kidney is sufficiently impaired that a large portion of the waste products and water are not removed from the blood, the life of the patient cannot be preserved unless a way is provided for artifically performing the function of the impaired kidney. Many new developments have come to light which perform the function of the impaired kidney extracorporeally. For example, see copending U.S. patent application Ser. No. 106,184, filed Jan. 13, 1971. Nevertheless, even with the existing improvements in extracorporeal kidney apparatus, the same general procedure is used for dialyzing patients' blood that was used very early in the treatment of kidney disease.
For example, the most commonly accepted practice for dialyzing a patient's blood extracorporeally requires the surgical creation of a subcutaneous, arterio-venous fistula. Thereafter, the subcutaneous venous system dilates secondary to the increase of blood flow derived from the artery to the vein through the fistula. Sufficient blood flow for dialysis is then obtainable by venipuncture with large bore needles. Normally, two hollow needles or cannulas with an internal stylet or trocar are used to perform two venipunctures on the patient so that two blood-communication sites exist simultaneously in the patient. Conventionally, blood is withdrawn from one of the punctured blood vessels, forced through a hemodialyzer and thereafter forced into the other.
The aforementioned procedure has been found to have serious disadvantages both to the patient and to the attending physicians and technicians. The problems are particularly aggravated because most patients requiring extracorporeal hemodialysis must undergo treatment as frequently as three to seven times per week. This means that if every venipuncture were completely successful, a patient would need to undergo from 6 to 14 venipunctures or cannulations each week.
It is well-known that the duration and well-function of a fistula created by venipuncture is inversely related to the number of venipunctures. Tissue repeatedly subjected to the trauma of venipuncture is much more susceptible to thrombophlebitis, paravascular hemorrhage, clotting and infection. In fact, it is commonly found in patients who have experienced a number of venipunctures, that the tissues surrounding the most accessible veins develop large hematomas which obscure the veins making successful venipuncture extremely difficult because of insufficient blood flow in the damaged blood vessels.
Also contributing to the problem is the fact that once one successful venipuncture is made and blood is allowed to flow from the patient's body toward a hemodialyzer, the blood volume in the patient's body is reduced making the second venipuncture very difficult. Historically, it has been found that while most skilled physicians or technicians are able to perform the first venipuncture with little difficulty, frequently a plurality of attempts is necessary before a second venipuncture can be performed on the same patient.
Additionally, while the pain and discomfort suffered by the patient is understandable, the multiple attempts at venipuncture often necessary to place the second needle results in increasing apprehension, and anxiety on the part of both the patient and the physician or technician attending the patient further reduces the likelihood of successful venipuncture.